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 NEW  Matt presents bias and operation data for the 6V6 tube in SE operation - 6V6 Single-Ended (SE) Ultra Linear (UL) Bias Optimization.

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 Post subject: 6V6 PP amp
PostPosted: 21 Oct 2019, 16:26 
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Joined: 06 Oct 2015, 22:05
Posts: 20
I've got the itch to build another amp. I was wondering what people's experiences were with this one:
http://diyaudioprojects.com/Schematics/ ... Amplifier/
if anyone has done it.


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 Post subject: Re: 6V6 PP amp
PostPosted: 21 Oct 2019, 17:59 
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Joined: 24 Nov 2010, 14:39
Posts: 33
Location: California
I built an amplifier like this (stereo). I used solid-state rectification, and have about 300 volts B+ to the output tubes. I used Edcor GXPP15-8K output transformers. I made a couple of changes that Bruce recommended. I upsized the coupling capacitors, from .1 uf to .22 uf. I increased the value of the electrolytic bypass capacitors, on the cathodes of the output tubes, from 47 uf to 470uf. There changes gave the amplifier much better bass response.

Since I had 12 volt heater voltage available on the power transformer, I used 12SL7 and 12V6 tubes. I kinda wanted to use NOS tubes (nostalgia), and the 12 volt heater versions are in much less demand that their 6-volt cousins, so they are very inexpensive about $6 each at AES. The amp wont exactly shake the walls, but it does sound really nice.


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 Post subject: Re: 6V6 PP amp
PostPosted: 21 Oct 2019, 19:36 
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Joined: 06 Oct 2015, 22:05
Posts: 20
thank you! Those are just the tips I'm looking for.

I'm thinking of using edcor transformers
CXPP10-8K

and for power:
XPWR008
600V (300-0-300) at 200mA center tapped, 6.3V at 4A and 5V at 3A.
or
XPWR081
70V (285-0-285) at 200mA center tapped, 6.3V at 6A and 5V at 5A.
for a lower voltage since the write-up mentioned the voltage being a bit high. I'll have to run some sims.


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 Post subject: Re: 6V6 PP amp
PostPosted: 21 Oct 2019, 20:31 
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Joined: 04 Jun 2008, 20:59
Posts: 4050
Location: Arizona, USA
Hi, The CXPP transformers should be fine. They are only rated for 10 watts, but really are over designed and are much better performers than the GXPP ones. Especially in th elow bass and top treble. You might also consider the CXPP25 size as they are really nice to and a bit more robust. I use them all the time. It would allow you to grow the amp if desired to use 6L6GC, KT77 and EL34s. Either of the power trannies will be fine with tube rectifiers. If you went to SS ones they would likely develop too much B+ for 6V6s and they would fry. The other tubes could handle it though.

Good listening
Bruce

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Some of my DIY Tube Amplifier Projects:


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 Post subject: Re: 6V6 PP amp
PostPosted: 21 Oct 2019, 21:52 
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Joined: 06 Oct 2015, 22:05
Posts: 20
great points. More to ponder as I do have a lot of 6L6GC tubes


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 Post subject: Re: 6V6 PP amp
PostPosted: 22 Oct 2019, 10:04 
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And of course after being happy that the transformers are pretty affordable for this design I find some Hashimoto HWC-30-8 ones that are awfully tempting.


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 Post subject: Re: 6V6 PP amp
PostPosted: 22 Oct 2019, 14:37 
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Joined: 06 Oct 2015, 22:05
Posts: 20
Looking at possibly going with Hammond because the 8 weeks production time for Edcor is getting close to bumping up against their holiday shutdown,which happened to me before.

Would 7.6K mess up much in place of 8K?
1650FA 25 7,600 ct 128 ma.

thanks,


gofar99 wrote:
Hi, The CXPP transformers should be fine. They are only rated for 10 watts, but really are over designed and are much better performers than the GXPP ones. Especially in th elow bass and top treble. You might also consider the CXPP25 size as they are really nice to and a bit more robust. I use them all the time. It would allow you to grow the amp if desired to use 6L6GC, KT77 and EL34s. Either of the power trannies will be fine with tube rectifiers. If you went to SS ones they would likely develop too much B+ for 6V6s and they would fry. The other tubes could handle it though.

Good listening
Bruce


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 Post subject: Re: 6V6 PP amp
PostPosted: 24 Oct 2019, 10:20 
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Joined: 06 Oct 2015, 22:05
Posts: 20
Ordered output transformers from Electraprint so the project is a go.


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 Post subject: Re: 6V6 PP amp
PostPosted: 24 Oct 2019, 11:06 
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Joined: 06 Oct 2015, 22:05
Posts: 20
I'm fairly new to PSUDII, am I doing this correctly?

As designed:
Attachment:
psud.jpg


With a choke instead:
Attachment:
psudchoke.jpg


I've read that chokes aren't really needed in push pull setups. Is it overkill?


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 Post subject: Re: 6V6 PP amp
PostPosted: 24 Oct 2019, 17:16 
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Joined: 06 Oct 2015, 22:05
Posts: 20
or I could add a soft start circuit and go SS (if my #s are correct) and get some really smooth DC

Attachment:
psud-ss.jpg


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